Polyurethane foams are widely used in thermal insulation applications, such as refrigerators, insulation for outdoor panels, and various parts of automobiles. The manufacture of polyurethane foam typically involves the mixing of chemical components, such as a polyol and an isocyanate, with the addition of blowing agent and other additives.
One common manufacturing method is to blend the blowing agent with a polyol compound first before allowing the mixture to react with an isocyanate to create polyurethane foam. Chlorofluorocarbons (CFCs), for example Freon 11 and Freon 12, were extensively used by the industry in the past decade as the primary blowing agent. They are considered as the 1st generation blowing agents and have been phased out under the UN Montreal Protocol due to their high Ozone Depletion Potential (ODP) value. Hydrochlorofluorocarbons (HCFCs), such as HCFC 141b, which are considered as the 2nd generation blowing agents are also scheduled to be phased out under the Montreal Protocol as its ODP value is not zero.
The 3rd generation of blowing agents to replace CFCs and HCFCs include compounds such as Hydrofluorocarbons (HFCs) (e.g. HFC-245fa, 365mfc, 134a), Hydrocarbons (e.g. cyclopentane), and Hydrofluoroolefins (HFO) (e.g. HFO-1234ZE). These blowing agents are mainly used in the manufacture of rigid polyurethane foam for insulation applications. The HFCs compounds are currently accepted by the industry as alternatives to CFCs and HCFCs but they are not direct replacements and the chemical formulations and mixing systems have to be adapted in order to achieve the required polyurethane foam properties.